Pipelines are used to transport fluids, such as oil and gas, to and from wells, refineries, and distributions centers. In order to maintain the structural integrity of a pipeline, physical properties within the pipeline are routinely tested, such as for example, fluid pressure, fluid flow rate, and corrosion/wear of the pipeline.
The technology for construction and operation of fluid transport pipelines has advanced significantly over the past several decades. For example, it is common practice to insert so-called “orifice fittings” at periodic intervals along a pipeline. Orifice fittings are described, for example, in U.S. Pat. Nos. 5,085,250 and 5,181,542, and are used to measure fluid pressure and flow rate. Typically, such orifice fittings are installed between two sections of pipe and feature a plate carrier that retains a removable orifice plate within a stream of flowing fluid within the pipeline. Orifice plates are typically in the form of disks that are dimensioned to fit within the plate carriers. The disks include a fluid aperture or opening that is smaller than the diameter of the pipeline. By measuring the fluid pressure upstream and downstream from the orifice plate, and calculating the difference between the upstream and downstream pressures, the rate of flow in the pipeline can be estimated.
In addition to testing for fluid pressure and flow rate, pipelines are often inspected for corrosion. Fluids carried by pipelines are often corrosive. As such, corrosion within a pipeline typically occurs from the inside out. Because it is difficult to examine the interior of a pipeline, corrosion coupons are inserted into the pipeline to estimate the amount of wear. After a predetermined amount of time, the corrosion coupons are removed from the pipeline and analyzed. By determining the degree of corrosion of the coupons, the degree of corrosion of the pipeline is estimated.
Coupon holders for inserting and removing corrosion coupons from a pipeline are described, for example, in U.S. Pat. Nos. 4,120,313 and 4,697,465. Typically, such coupon holders are large cylindrical housings that are mounted over small openings in the upper wall of the pipeline. In order to install a coupon holder, an appropriately sized opening must be located along the pipeline that corresponds to the particular coupon holder to be installed. Once an opening is located, the flow of fluid within the pipeline must be shut down in order to relieve the pressure within the pipeline so that the opening can be unplugged. Therefore, in addition to the difficulties associated with locating a suitable opening, installation of additional equipment requires that the pipeline be shut down, which is often impractical or a costly interruption.
Notwithstanding the common place nature of orifice fittings in gas pipelines and the regularity of corrosion testing using coupons, the two technologies have escaped combination. There still exists a need in the art for a device for testing corrosion in a pipeline that can be quickly and easily inserted and removed from the pipeline with minimal labor and minimal cost. While prior art coupon holders possess the ability to retain a corrosion coupon in the flow of fluid within a pipeline, the use of such coupon holders involves the arduous and time-consuming task of installing new equipment, potentially at multiple locations along the pipeline.